Ultraviolet light sources, such as mercury arc lamps and solid-state UV light sources comprising arrays of light-emitting diodes (LEDs) are commonly used for curing in coatings, inks, and adhesives in the imaging, printing, and telecommunication industries. LED technology is replacing traditional mercury arc lamps because they are more energy efficient, last longer, have lower operating temperatures, are safer and more environmentally friendly to use, can be manufactured more compactly, among other reasons.
LEDs and other types of light sources may be characterized as exhibiting a Lambertian or near-Lambertian emission pattern. Accordingly, one challenge with UV curing is providing a uniform irradiance of light across an entire target object or surface. In particular, curing of large two-dimensional surfaces may require manufacture of large light sources that are costly and cumbersome, or may require combining multiple light sources to provide irradiance over the target surface area. The inventor herein has recognized a potential issue with the above approaches. Namely, irradiance uniformity may be poor, especially near edges of emission patterns of individual light sources and at junctions between multiple light sources.
One approach that addresses the aforementioned issues includes a light source comprising a cylindrical lens, for example a cylindrical Fresnel lens, and a linear array of light-emitting elements aligned with and emitting light through the cylindrical Fresnel lens, wherein the cylindrical Fresnel lens reduces the angular spread of light in a widthwise axis of the linear array, the linear array spanning a lens length. Furthermore, the light source may comprise a housing, wherein a window may be mounted in a front plane of the housing, the window length spanning a front plane length, and wherein first and last light-emitting elements of the linear array are positioned adjacent to widthwise edges of the window, and wherein window sidewalls at the widthwise edges are aligned flush with the housing sidewalls. In this manner, emission pattern uniformity of the light source can be enhanced for an individual light source and across multiple light sources as compared to conventional light sources.
It will be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.